[PATCH] x86: Disable RTM on Skylake [BZ #27398]

[H.J. Lu]

On Sat, Mar 27, 2021 at 12:15 PM Florian Weimer <fw@deneb.enyo.de> wrote:
>
> * H. J. Lu via Libc-alpha:
>
> > Disable RTM explicitly on Skylake since CPUID may incorrectly report RTM
> > feature.
> > ---
> >  sysdeps/x86/cpu-features.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
> > index d7248cbb45..3641a48407 100644
> > --- a/sysdeps/x86/cpu-features.c
> > +++ b/sysdeps/x86/cpu-features.c
> > @@ -518,6 +518,10 @@ init_cpu_features (struct cpu_features *cpu_features)
> >                with stepping >= 4) to avoid TSX on kernels that weren't
> >                updated with the latest microcode package (which disables
> >                broken feature by default).  */
> > +         case 0x8e:
> > +         case 0x9e:
> > +           /* Disable RTM explicitly on Skylake since CPUID may report
> > +              RTM feature incorrectly [BZ #27398].  */
> >             CPU_FEATURE_UNSET (cpu_features, RTM);
> >             break;
> >           }
>
> Won't this affect the server parts as well?  I'm not sure if that's
> what our users want.

No since Xeon has a different model number (0x55).

> We need to report the kernel bug properly, it got stalled because we
> initially suspected it might be a security bug.



-- 
H.J.